The invention relates to the field of high flow low pressure suction device based on non-contact suction mechanisms. These devices have found profound use in mobile robots that are capable of moving on all surfaces regardless of the orientation. Wall climbing robots have commercial uses in making wall painting robots, window cleaning robots, surveillance robots, solar panel cleaning robots, inspection robots in nuclear plants and many any other robotic systems that need to move on upside down surfaces, vertical surfaces or extremely slant surfaces.
Many technologies for adhesion to the surface have been developed like magnetic systems, electrostatic systems etc. each having its own advantages and disadvantages. Of these, the fluid based suction technology can handle a variety of surfaces irrespective of the material nature of the surface. The fluid based suction technology can be widely classified into two categories namely, contact suction systems (use a flexible seal between the robot and the surface) and non-contact systems. The contact systems or suction cups are generally more efficient in terms of force produced per unit energy used. However, these systems are not fit for mobile robots especially on rough surfaces. Suction cups are used in walking like robots and in wheeled robots with dragged seals. This technology faces several problems. One of the major problems is the friction between the rubber skirt (seal (in dragged seal form)) and the surface. This hinders motion and may also leave rubber marks on walls. Also, if due to certain non-uniformity in the surface (on which the robot is moving) the seal leaves contact then the air pressure will be lost and catastrophic failure will result (applicable for both, dragged seal type and the walking type). Flexible and segmented seals have been used to reduce problems on rough surfaces like in U.S. Pat. Nos. 4,095,378, 4,809,383 and 5,014,803, but these are effective to a limited extend only.
The non-contact suction systems are superior to the contact suction systems in context to mobile robots but inherently use much more energy per unit force produced. These systems from prior art are usually based on Bernoulli's principle for creating low pressure. This means they use a large portion of the under surface as a flat surface as in US20110192665A1. The under surface of the suction mechanism/mobile robot in conjugation with the sucked surface forms a venturi duct, as in US20060144624. The device of the present invention does not have a flat under surface and hence the under-surface in conjugation with the sucked surface does not form a venturi duct. The Bernoulli's principle based mechanisms can produce suction from both inward flow of the fluid and outward flow of the fluid and this is a key differentiator in identifying a Bernoulli's principle based system from the device of the present invention. Many prior arts that use the outward flow of air like US20110192665A1 using pressurized air can be found.
The other class of non-contact suction mechanisms is the vortex attractors. These usually have the underbody comprising almost completely of an impeller what pushes the air (or other fluid) out of the region between the underbody and the sucked surface and hence creates a low pressure in the region. The flow is like a vortex. U.S. Pat. Nos. 5,194,032 and 6,565,321 are some examples of vortex attractors. These have high moment of inertia for the impeller and hence have lower response time and huge gyroscopic precession. Also, they always operate in the risk of the impeller striking some surface protrusion hence damaging the surface and the impeller.
The invention described presently uses a radically new approach to creation of suction that is turbulence based suction. The present invention is a non-contact suction mechanism based suction device and hence has superior rough surface performance in comparison to a contact suction mechanism based suction device. The present invention has higher energy efficiency than a Bernoulli's principle based suction device. Also, the mechanism and device has lower sensitivity to surface protrusions as compared to a Bernoulli's principle based suction device/apparatus.